allow rcu in scheduler kthread

d6952037 · Nickolai Zeldovich · 1229ed4b · d6952037 · d6952037
--- a/proc.c
+++ b/proc.c
@@ -488,13 +488,17 @@ void
 scheduler(void)
 {
  struct proc *p;
-  int pid;

-  pid = ns_allockey(nspid);
+  // allocate a fake PID for each scheduler thread
+  struct proc *schedp = allocproc();
+  if (!schedp)
+    panic("scheduler allocproc");
+
+  proc = schedp;

  // Enabling mtrace calls in scheduler generates many mtrace_call_entrys.
  // mtrace_call_set(1, cpu->id);
-  mtrace_fcall_register(pid, (unsigned long)scheduler, 0, mtrace_start);
+  mtrace_fcall_register(schedp->pid, (unsigned long)scheduler, 0, mtrace_start);

  for(;;){
    // Enable interrupts on this processor.
@@ -524,17 +528,17 @@ scheduler(void)
      p->state = RUNNING;
      p->tsc = rdtsc();

-      mtrace_fcall_register(pid, 0, 0, mtrace_pause);
+      mtrace_fcall_register(schedp->pid, 0, 0, mtrace_pause);
      mtrace_fcall_register(proc->pid, 0, 0, mtrace_resume);
      mtrace_call_set(1, cpu->id);
      swtch(&cpu->scheduler, proc->context);
-      mtrace_fcall_register(pid, 0, 0, mtrace_resume);
+      mtrace_fcall_register(schedp->pid, 0, 0, mtrace_resume);
      mtrace_call_set(0, cpu->id);
      switchkvm();

      // Process is done running for now.
      // It should have changed its p->state before coming back.
-      proc = 0;
+      proc = schedp;
      release(&p->lock);
      break;
    }

--- a/rcu.c
+++ b/rcu.c
@@ -97,7 +97,7 @@ rcu_delayed(void *e, void (*dofree)(void *))
 void
 rcu_begin_read(void)
 {
-  if (proc->rcu_read_depth++ == 0)
+  if (proc && proc->rcu_read_depth++ == 0)
    proc->epoch = global_epoch;
  __sync_synchronize();
 }
@@ -105,7 +105,7 @@ rcu_begin_read(void)
 void
 rcu_end_read(void)
 {
-  if (--proc->rcu_read_depth == 0)
+  if (proc && proc->rcu_read_depth > 0 && --proc->rcu_read_depth == 0)
    proc->epoch = INF;
 }